[1] Bed form geometry and dynamics in a straight section of the Elbe River in Germany is analyzed considering the measured bed surfaces as two-dimensional random fields of bed elevations. Statistically derived roughness parameters are evaluated from highresolution digital elevation models, which were available for a range of flow rates from low flows to floods. The key results relate to the identification of characteristic scaling regions in the bed surface spectra, and to observed relationships between water discharge and both the standard deviation and a factor of the "−3" spectral law of bed elevations. Two-dimensional second-order structure functions of bed elevations are also analyzed to gain further insight into the spatial structure of sand wave beds. In addition, the interrelations between flow rate hysteresis and the statistical structure of bed forms, as well as effects of channel modification by groynes, are highlighted and discussed. The reported results demonstrate that statistical parameters of bed forms may be used for characterization and prediction of flow-dependent sand bed roughness.Citation: Aberle, J., V. Nikora, M. Henning, B. Ettmer, and B. Hentschel (2010), Statistical characterization of bed roughness due to bed forms: A field study in the Elbe River at Aken, Germany, Water Resour. Res., 46, W03521,

No abstract

Despite ubiquitous warming, the lower Oder River typically freezes over almost every year. Ice jams may occur during freeze-up and ice cover breakup phases, particularly in the middle and lower reaches of the river, with weirs and piers. The slush ice and ice blocks may accumulate to form ice jams, leading to backwater effects and substantial water level rise. The small bottom slope of the lower Oder and the tidal backflow from the Baltic Sea enhance the formation of ice jams during cold weather conditions, jeopardizing the dikes. Therefore, development of an ice jam flood forecasting system for the Oder River is much needed. This commentary presents selected results from an international workshop that took place in Wrocław (Poland) on 26–27 November 2018 that brought together an international team of experts to explore the requirements and research opportunities in the field of ice jam flood forecasting and risk assessment for the Oder River section along the German–Polish border. The workshop launched a platform for collaboration amongst Canadian, German and Polish scientists, government officials and water managers to pave a way forward for joint research focused on achieving the long-term goal of forecasting, assessing and mitigating ice jam impacts along the lower Oder. German and Polish government agencies are in need of new tools to forecast ice jams and assess their subsequent consequences and risks to communities and ship navigation along a river. Addressing these issues will also help research and ice flood management in a Canadian context. A research program would aim to develop a modelling system by addressing fundamental issues that impede the prediction of ice jam events and their consequences in cold regions.

Groynes help to protect river banks and support water levels for navigation. Since recently, groyne fields are considered as surrogate habitat for various species and may, in terms of ecology, partially replace flood plains that were lost in the course of river training in the last centuries. In order to maintain and improve the hydraulic function and ecological value of groyne fields, the German Federal Institutes of Hydrology and the Waterways Engineering and Research studied innovative groyne types and regular groynes on the River Elbe, Germany. In a 10-year field campaign, groyne field hydraulics and morphology were monitored using acoustic Doppler current profiler and echo-sounding techniques. The data is used to assess groyne field heterogeneity and morphodynamics over the 10-year period as well as flow patterns at different flow stages. The results indicate a high morphological activity in the groyne fields associated with flood discharges. Significant sedimentation in the bank regions was observed, whereas sedimentation in deeper areas of the groyne fields was less pronounced. The sedimentation patterns and rates in the groyne fields are, to some extent, found to be influenced by different groyne types and associated flow patterns.

No abstract